Batteries, such as sodium batteries, having a metal chloride cathode are known to constitute useful rechargeable energy sources having high energy and power density properties. While sodium-sulfur batteries have proven useful, they have been found to have certain shortcomings.
In particular, known sodium-sulfur batteries experience significant corrosion problems, due to higher operating temperatures, and present safety hazards Sodium-sulfur batteries also suffer from degradation of solid electrolytes in polysulfide melts.
Recently, sodium batteries with metal chloride cathodes have attracted interest because they appear to offer energy densities comparable to those of sodium-sulfur batteries, but are less subject to the above-described drawbacks. Energy density is here defined as the open-circuit voltage of the battery multiplied by its coulombic capacity in ampere-hours, divided by the weight of the electrodes.
Among the various metal chlorides which have been investigated for use as cathodes, nickel chloride has been found to be worth considering because it provides an energy density higher than that of ferrous chloride and presents a good resistance to overcharge.
Various approaches to the fabrication of the positive electrode, or cathode, of such a battery have included: producing a porous metal body by sintering a metal powder in a reduced atmosphere and then chlorinating the metal body; impregnating a metal matrix with a brine solution of sodium chloride and assembling the battery in the discharged state; sintering a mixture of metal powders and a slurry of sodium chloride in brine; and sintering dry powders of metal and sodium chloride. Subsequent to fabrication, the electrode must be converted to active form electrochemically to form NiCl.sub.2.
Thus, formation of such an electrode entails a number of steps. Moreover, particularly if the electrode is formed by sintering metal powder and sodium chloride together, the resulting electrode may not exhibit great mechanical strength. Therefore, the electrode is subject to failure due to mechanical stresses induced therein during successive charging and discharging cycles.